Traveller Diarrhoea

Traveller diarrhoea is diarrhoea (3 or more loose stools in 24 hours) with at least one other symptom (abdominal cramps, nausea, vomiting, fever, urgency or blood in the stool) that begins during travel or within 10 days after return, usually from a region with limited sanitation. It affects 20 to 60% of travellers to high risk regions (South and Southeast Asia, Africa, Central and South America, the Middle East) in 2 weeks.

• Cause: bacterial pathogens account for 80 to 90% of cases. Enterotoxigenic Escherichia coli is the commonest (30 to 40%), followed by enteroaggregative E. coli, Campylobacter jejuni, Shigella, non-typhoidal Salmonella, Aeromonas, Plesiomonas, and Vibrio species. Viruses (norovirus, rotavirus) cause 5 to 10%, and parasites (Giardia lamblia, Cryptosporidium, Entamoeba histolytica, Cyclospora cayetanensis) cause 5 to 10%, but a larger proportion with persistent illness. Multiple pathogens are found in up to 20% of cases.
• Transmission is by food and water contaminated with human or animal faeces: raw or undercooked meat and seafood, salads, unpeeled fruit, tap water, ice, unpasteurised dairy, and street food.
• Risk factors: young adult travellers, a destination in a high risk region, adventurous eating, a history of previous travellers' diarrhoea, reduced gastric acid (proton pump inhibitors, antacids, gastric surgery), immunosuppression, inflammatory bowel disease, and young children.
• Onset is usually in the first week of travel (median 3 to 5 days after arrival). The illness lasts 3 to 5 days if untreated (1 day with early antibiotics), and 10% last more than a week. About 3% develop persistent diarrhoea beyond 2 weeks, and 3 to 17% develop post-infectious irritable bowel syndrome within 6 months.
• Complications: dehydration, electrolyte disturbance, reactive arthritis, Guillain-Barre syndrome (after Campylobacter), haemolytic uraemic syndrome (after Shiga toxin producing E. coli), post-infectious irritable bowel syndrome, lactose intolerance, and bacteraemia in the immunosuppressed.

• Sudden onset of watery stools (3 to 10 per day), with abdominal cramps, nausea, bloating, urgency and, in about 10 to 20%, fever and vomiting. Dysentery (blood and mucus in stool, fever, tenesmus) suggests Shigella, Campylobacter, Salmonella, enteroinvasive E. coli or Entamoeba histolytica.
• Features that suggest the cause:
  • Watery diarrhoea with cramps, no fever: enterotoxigenic E. coli.
  • Fever, bloody or mucoid stool, tenesmus: Shigella, Campylobacter, Salmonella.
  • Vomiting predominant, short illness of 1 to 3 days: norovirus.
  • Rice water stools in large volumes: Vibrio cholerae.
  • Foul sulphurous belching, flatulence, bloating and weight loss, onset 1 to 2 weeks after exposure, lasting weeks: Giardia.
  • Subacute watery or bloody diarrhoea with weight loss lasting weeks, from endemic regions: Entamoeba histolytica, Cyclospora, Cryptosporidium.
• Dehydration signs: thirst, dry mucosa, reduced urine output, postural dizziness, tachycardia, sunken eyes, reduced skin turgor, low blood pressure, and confusion.
• Differential diagnosis: malaria (fever in a traveller from an endemic area must be tested for malaria, even with diarrhoea), typhoid and paratyphoid fever, hepatitis A, acute HIV infection, Clostridioides difficile, inflammatory bowel disease, food poisoning from preformed toxins (Staphylococcus aureus, Bacillus cereus), appendicitis, medicines (antimalarials, antibiotics) and amoebic liver abscess.
• Red flags: bloody diarrhoea with high fever (above 39 C), severe dehydration, persistent vomiting preventing oral rehydration, severe abdominal pain or distension, diarrhoea lasting more than 14 days, signs of sepsis, age above 65 years, immunosuppression, pregnancy, return from a malaria endemic area with fever, neurological features (weakness, paraesthesia), and passage of very little urine.

• Clinical, based on the travel history (destination, dates, food and water, activities, contacts, prophylaxis), the stool pattern, and the presence of fever, blood and dehydration. Most mild cases need no tests.
• Assess dehydration (pulse, blood pressure, capillary refill, mucosa, weight). Check temperature.
• Investigate when there is fever, blood in the stool, severe illness, persistence beyond 7 days, immunosuppression, or onset after return:
  • Stool culture, and a multiplex polymerase chain reaction panel for bacterial, viral and protozoal pathogens, with microscopy for ova, cysts and parasites (examine three samples on different days when Giardia or Entamoeba is suspected). Giardia and Cryptosporidium antigen tests are sensitive.
  • Stool test for Clostridioides difficile toxin when there has been recent antibiotic use or hospital contact.
  • Full blood count, urea, creatinine and electrolytes, glucose, C-reactive protein, and blood cultures when febrile and unwell.
  • Malaria thick and thin films or a rapid test for any fever after travel in an endemic region, and typhoid blood cultures.
  • Faecal calprotectin and endoscopy for persistent diarrhoea, when inflammatory bowel disease is possible.
  • Hepatitis A serology and HIV testing as indicated.
  • Abdominal ultrasound for suspected amoebic liver abscess (right upper quadrant pain and fever).
• Test for coeliac disease, lactose intolerance, bile acid diarrhoea, and small intestinal bacterial overgrowth in persistent post-infectious symptoms.

• Fluids are the foundation of treatment:
  • Oral rehydration solution with glucose and electrolytes (sodium 75 mmol/L, glucose 75 mmol/L, total osmolarity about 245 mOsm/L): adults 200 to 400 mL after each loose stool, or 2 to 3 L per day, sipped regularly. In mild disease, safe fluids (boiled or bottled water, clear soups, diluted juice) and salty foods are enough.
  • Severe dehydration or inability to drink: intravenous Ringer lactate or 0.9% sodium chloride 20 to 30 mL/kg over the first 30 to 60 minutes, reassessing, then replace the deficit over 3 to 6 hours.
  • Continue feeding with normal diet (bananas, rice, toast, potatoes, soup) and avoid alcohol, caffeine, fatty and highly spiced foods, and raw vegetables during illness.
• Symptomatic therapy (non-bloody diarrhoea without high fever):
  • Loperamide 4 mg orally at first, then 2 mg after each loose stool (maximum 16 mg per day for prescription use, 8 mg per day without prescription supervision), for no more than 48 hours. It reduces diarrhoea duration by about 1 day, and can be combined with an antibiotic. Do not use in bloody diarrhoea, high fever, children under 12 years, or suspected severe colitis, and stop with abdominal distension.
  • Bismuth subsalicylate 524 mg (30 mL) orally every 30 to 60 minutes up to 8 doses in 24 hours, for 2 days, reduces stool frequency by about 40%. Avoid in aspirin allergy, renal impairment, pregnancy, anticoagulation, children, and with doxycycline. It turns the stool and tongue black.
  • Ondansetron 4 mg orally or sublingually 8 hourly for vomiting (child 0.15 mg/kg), and oral analgesia with paracetamol 1 g 6 hourly for cramps. Avoid NSAIDs in dehydration.
  • Racecadotril 100 mg orally 8 hourly (child 1.5 mg/kg per dose) is an alternative anti-secretory drug where available.
• Antibiotics are used for moderate to severe illness (disruption of the planned itinerary, 4 or more loose stools per day, fever, or bloody stool) and for high risk patients:
  • Azithromycin 500 mg orally once daily for 1 to 3 days (or a single 1 g dose), the preferred drug for dysentery, fever or illness acquired in South and Southeast Asia, where fluoroquinolone resistance is high. Child 10 mg/kg once daily for 3 days (maximum 500 mg).
  • Ciprofloxacin 500 mg orally 12 hourly for 1 to 3 days (or a single dose of 750 mg), only when the destination has low fluoroquinolone resistance (not Southeast Asia or the Indian subcontinent), and in the absence of risk factors for tendon, neurological and cardiac adverse effects. Children and pregnancy: avoid when alternatives exist.
  • Rifaximin 200 mg orally 3 times daily for 3 days for non-invasive watery diarrhoea, with no fever or blood (not effective for invasive pathogens such as Campylobacter, Salmonella and Shigella). Fluoroquinolone and rifaximin have limited use with high resistance.
  • Cholera: doxycycline 300 mg once, or azithromycin 1 g once, with aggressive rehydration.
  • Antibiotic therapy for Shiga toxin producing E. coli (suspected by bloody diarrhoea without fever) is avoided because of the risk of haemolytic uraemic syndrome.
• Specific parasites:
  • Giardiasis: tinidazole 2 g orally once with food, or metronidazole 400 mg orally 3 times daily for 5 days (child 5 mg/kg 8 hourly), or nitazoxanide 500 mg 12 hourly for 3 days. Repeat the treatment, or use a different drug, for persistent infection.
  • Amoebic dysentery or liver abscess: metronidazole 800 mg orally 8 hourly for 5 to 10 days (child 10 mg/kg 8 hourly), followed by a luminal agent to clear cysts (paromomycin 25 to 35 mg/kg per day in 3 divided doses for 7 days). Avoid alcohol with metronidazole and tinidazole for 48 hours.
  • Cryptosporidium: nitazoxanide 500 mg orally 12 hourly for 3 days (child 1 to 3 years 100 mg 12 hourly, 4 to 11 years 200 mg 12 hourly), with supportive care and treatment of HIV.
  • Cyclospora: co-trimoxazole 960 mg orally 12 hourly for 7 to 10 days.
• Prevention:
  • Food and water precautions: choose food that is cooked and served hot, drink bottled or boiled water or water treated by filtering and chlorine, avoid ice, raw salads, unpeeled fruit and unpasteurised dairy, and wash hands with soap before eating (alcohol hand rub with 60% or more alcohol when soap is not available).
  • Bismuth subsalicylate 524 mg orally 4 times daily (with meals and at bedtime) for up to 3 weeks reduces risk by about 50%. Antibiotic prophylaxis (rifaximin 200 mg once or twice daily) is considered only for high risk travellers (immunosuppression, inflammatory bowel disease, short critical trips), with a discussion of resistance and adverse effects.
  • Vaccination: oral cholera vaccine, typhoid vaccine, and hepatitis A vaccine are given before travel to appropriate destinations.
  • Take a self-treatment kit (oral rehydration salts, loperamide, and a single dose antibiotic if recommended) on trips to high risk areas.
• Special groups:
  • Children: the priority is rehydration with oral rehydration solution (50 mL/kg over 4 hours for mild to moderate dehydration, then 10 mL/kg after each loose stool), continued breast or normal feeding, and zinc 20 mg daily for 10 to 14 days (10 mg in infants under 6 months). Avoid loperamide and bismuth. Use azithromycin when an antibiotic is needed. Urgent review for lethargy, persistent vomiting, bloody stool, fever in infants under 3 months, and reduced urine output.
  • Pregnancy: oral rehydration, and azithromycin 500 mg once daily for 1 to 3 days when an antibiotic is needed. Avoid fluoroquinolones, bismuth subsalicylate, and metronidazole in the first trimester when possible. Loperamide only for short use after the first trimester.
  • Elderly: lower threshold for admission and intravenous fluids, avoid loperamide in severe disease, and monitor electrolytes and renal function.
  • Immunosuppressed (HIV, transplant, chemotherapy): early culture and polymerase chain reaction testing, early treatment with antibiotics, and a low threshold for admission.
  • Inflammatory bowel disease: exclude infection before attributing symptoms to a flare, and treat infection.
  • Renal impairment: adjust doses (for example ciprofloxacin and metronidazole), avoid NSAIDs, and monitor electrolytes.
• Follow up: expect improvement in 48 to 72 hours with treatment. Review those with persistent diarrhoea beyond 7 days (tests for parasites and Clostridioides difficile) and beyond 14 days (assess for Giardia, post-infectious irritable bowel syndrome, lactose intolerance, coeliac disease and inflammatory bowel disease). Refer to infectious diseases or gastroenterology for persistent symptoms, immunosuppression, or severe illness.